Volume control system for radioreceivers



23, 1933- E. R. HENTSCHEL 1,909,954

VOLUME CONTROL SYSTEM FOR RADIORECEIVERS Filed Aug. 9, 1930 fif 26 l'l l l l'l l'l l l l INVENTOR.

A TTORNE Patented May 23, 1933 UNITED STATES PATENT 0pm: j

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- v runumrsrnauzon or sun ERNEST n. HENTSCHEL, nncnnsnn, nssronon rowrrmn mm, me, on NEW YORK, n. Y., a conron-Anonor DELAWARE VOLUME common srs'rmvr'ronnanronncnrvnas Application filed August '9, 1930. Serial 1704474306.

My invention relates broadly to radio receiving circuits and more particularly to an automatic volume control circuit for radio receivers, whereby the volume of reproduced sound may be maintained substansially uniform independently of sudden increases in volume which occur due to fading effects at a receiver, when operating with respect to a distant broadcasting transmitter.

One of the objects of my invention is to provide a simplified form of volume control circuit, in which the output of the audio frequency amplifier is rectified and applied to a control device for effecting a detuning of the radio frequency amplification system in the receiver, whereby the amplitude of reproduced sound may be decreased in the event that the signaling energy tends toincrease due to fading effects.

-Another object of my invention is to'ipro vide a circuit arrangement for a volume con trol system in which a rectifier circuit operates in accordance with a predetermined signal level at the reproducer, and the energy thus derived utilized to actuateia detuning device in the radio frequency amplification system of the radio receiver for maintaining the volume of reproduced sound substantially uniform.

"Still another object of my invention is to provide an arrangement of rectifier circuit adapted to be connected into a selected position' in a radio broadcast receiving system, for developing control impulses for actuating a detuning mechanism and correspondingly controlling the selectivity of the radio receiving circuit according to the amplitude of reproduced sound whereby the sound reproduced by the receiver is maintained substantially constant independent of fading effects.

A further object of my invention is to provide a circuit arrangement for coupling a rectifyingwelement into a broadcast receiver in such a position that energy may be derived for operating a detuning device, and maintaining the volume of reproduced sound substantially constant'at the receiver independent of fading effects.

.xOther and further objects of my invention reside in the circuit arrangement for arecti fying element in a volume control circuit for a radio receiver asset'forth more fully in the specificationhereinafterfollowing by reference to the accompanying drawing, 'in which:

'Figure 1- diagrammatically illustrates a radio broadcast receiver showing the application of the volume control circuit of my .inventionthereto; Fig. 2 illustrates a modilied form of control circuit for anamplificatlon system connected accordmg to my in ventiong and Fig. 3 illustrates a further modified formof frequency control device emp10yed in the volume control system of my invention.' i I My-invention is directed to a method for automatically operating'a volume control devicebymeans of direct current obtained by rectifying thealternating' current of either audio or radiofrequency,which varies according to the amplitude of the incoming signaling energy; 7 I 5 In Fig-1, I have showna radio receiver employing onestage of radio frequency, a detector and two stages of audio frequency.

If desired, more stagesmay be used, and different'types' may be employed. The ,radio frequency amplifier-has been desi nated at 1, the detector at 2, and the audio requency amplifier at 3 and 4. 'P'ower supply for the several circuits has been designated generally at 28. Parts represented: by numerals 5 and 6 constitute alight condenser operated by a-direct current device. This deviceis shown in more detail in my 'copendin'g application Serial No. 474,779 filed August '12, 193O, entitled volume'flcontrol system for radio receivers. Numeral 71refers to a rectifier using a direct currentjvoltage on the plateand a highly biased grid, so as to block the tube with noexcitation on the grid. 8 designates an audio frequency by-pass condenser, and 9 is an audio frequency choke. Condenser 25 serves as a coupling element forestablishing "a path between the plate of the amplifier "4: .tothe grid of rectifier tube 7 r speaker 10 becomes high,'and therefore,' the audio frequency voltage across the speaker When the: volumeof signal-in the loud also high, the pulsations, which are transmitted to the grid of rectifier tube 7, cause the plate current of this tube to increase. The plate current flows through part 5 of the device mentioned above, and rotates condenser 6. When the condenser is rotated, the tuned radio frequency circuit 11 of which it is a part is detuned, and the energy decreased,

thus decreasing the output of the receiver. It is possible to choose a certain value'of signal intensity at which this control begins to take effect by adjusting the bias on the grid of rectifier 7, so that the plate is blocked until this value is reached. The rotating part of condenser 6 is damped, so that it will take a defin ime nter al s as fo xampl abo t one s c nd for i to r t t su ie ently to au e a not c bl h nge in v lme, in. order that its motion will not follow ordinary varietieus n o nd mpli u e. Th s an be done by magnetic means, by one of the metho s n whic l quids flow h ough small openings, or by submerging thedevice in vis o o l.

7 Alt o gh he o ume c ntr l c n enser is,

shown in the circuit of the first tube 1, it could b p a ed. n any radi f eq ncy tube i cu r in. t a na a sc ibed in my op n ing pp i a on Serial No. 474,779 filed August 12, 193(7). In fact, it will give quicker action if placed elsewhere-because the antenna 12, beingcoupled to-the first t n f m r 1 b oadens the tuning Some- W t. If th rcuit tunes sha ply,,a small hang in capa i y of ondenser 6 will give a greate i c ea i gnal- As des rib s ar, th peratio of the device depends on the amplitude of the audio frequency currents, and the amplitude of the carrier wave affects the control only insofar as the greater amplitude of the carrier wave brings. in a gre er mpli de of the audio frequency component. If it is desired to depend only on the amplitude'of the radio frequeuey ier, he ctifier m y be onnected as shown in Fig. 2, which shows the detector cir ui y. .This circuit is chosen because it has themost radio frequency energy as it is the last amplification stage. 2 is the detector tube and 15 its tuned circuit. 16 is. a rectifier of the same type as shown at 7, in Fig. l,except that a resistor 18 is used in place of a choke. 19 designates a direct currentemnl fier f h u l type having potential source 26 for biasing the grid of tube 19. Condenser 2'1" serves to by-pass pulsations passed by rectifier 16. When direct current flows through resistance 20, a greater change in cur-rent occurs in the plate of tube 19 and lines 21 which go to the operating partof the volume control device. This direct current amplifier is shown so as to indicate a method for obtaining more power- If the control device is light and has little friction, the extra amp fi at on will notbe needed.

A combination of radio frequency and audio frequency control is obtained by combining the two methods here shown. This may be done by putting two windings in the armature of the control device, and connecting one to each of the rectifiers described.

Although a radio receiver is shown, a modification of the first method disclosed has uses in other types of apparatus, such as public It is understood that other types OfIQQtI. fiers may be used, and it may be possible to use this control device to operate othertypes of volume control apparatus, 7

In each of the control circuits, the output of the rectifier tube contains the condenser 8, The potential drop across condenser .8 is in reality the potential drop across the actuating winding of the volume control device which has been indicated en bloc, at 5 Direct current fiows along the line 21 to control the actuating winding of the olume control device, while the alternating current component passes through condenser 8 in the output circuit of the rectifier tube in the arrangement shown in Fig. 1.

In the circuit of Fig.2, there is a radio frequency component, which is passed through condenser 8, While the direct current component flows along line 21 for the control of the actuating winding of the vole urne control device. I

While I have described my invention in certain preferred embodiments, I'desire that it be understood that modifications may be made and that no limitationsupon my invention are intended other than are imposed I by the scope of the appended claims.-

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A radio broadcast receiver including aradio frequency amplifieiya detector, and an audio frequency amplifier, a radio frequency energy collecting circuit connected with said radio frequency amplifier, an auxiliary rectifier, connected to the output of said audio frequency amplifier, and'means controlled by said auxiliary rectifier for effecting adetuning of said radio frequency amplifier when the volume of reproducedsound exceeds a predetermined signal level.

2. A radio broadcast receiving circuit including a radio frequency amplifier portion,

a detector connected therewith, an audio frequency amplifier portion connected with said detector, a radio frequency energy collecting circuit connected with said radio frequency amplifier portion, a sound reproducer connected with said audio frequency amplifier portion, an auxiliary rectifier con nected to the output of said audio frequency amplifier portion, a variable capacity element connected with said radio frequency amplifier portion and a motor device for rotatably adjusting said variable capacity element controlled by the output of said auxiliary rectifier for controlling the amount of energy transferred from said radio frequency energy collecting circuit to said detector according to the amplitude of signaling energy in the output circuit of said audio frequency amplifier portion. 7

3. A radio broadcast receiver including a radio frequency amplifier, a detector, and an audio frequency amplifier, a radio frequency energy collecting circuit connected with said radio frequency amplifier, an auxiliary rectifier connected to frequency amplifier, and means actuated bv said auxiliary rectifier for effecting a detuning of said radio frequency amplifier when the volume ofreproduced sound ex: ceeds a predetermined signal level, said auxiliary rectifier being biased to remain inoperative for all values of signal current.

below said predetermined signal level.

4. A radio broadcast receiver including a radio frequency amplifier, a detector, and an audio frequency amplifier, a radio frequency energy collecting circuit connected with said radio frequency amplifier, an auxiliary rectifier connected to the output of said audio" frequency amplifier, and highly damped means responsive to changes in energy in the output circuit of said auxiliary rectifier for effecting a detuning of said radio frequency amplifier when the volume of the reproduced sound exceeds a predetermined signal level.

5. A radio broadcast receiving circuit including a radio frequency amplifier portion,

a detector connected thereto, an audio frequency amplifier portion connected with said detector, a radio frequency energy collecting circuit connected with said radio frequency amplifier portion, a sound reproduce! connected with said. audio frequency amplifier portion, an auxiliary rectifier connected to the output of said audio frequency amplifier portion, and means including a variable impedance device connected in circuit with said radio frequency amplifier portion and controlled by the output of said auxiliary rectifier for controlling the amount of energy transferred from said radio frequency energy collecting circuit to said detector on a selected frequency according to the amplitude of signaling energy in the output circuit of said audio frequency amplifier portion.

the output of said audio 6. A radio broadcast receiver including a radio frequency amplifier, a detector, and an audio frequency amplifier, a radio frequency energy collecting circuit connected with said radio frequency amplifier, an auxiliary rectifier, said auxiliary rectifier having its input terminals connected'across the output termi-* nals of said audio frequency amplifier and means controlled by the output circuit of said auxiliary rectifier for effecting a detuning of said radio frequency amplifier when the volume of reproduced sound exceeds a predetermined signal level. y

7 A radio broadcast receiver including a radio frequency amplifier, a detector, and an audio frequency amplifier, a radio frequency energy collecting circuit connected with said radio frequency amplifier, an auxiliary rectifier, said auxiliary rectifier having its input terminals capacitively coupled with the out ut circuit of said audio. frequency ampli er and means controlled by the output circuit of said auxiliaryrectifier for effecting a detuningof said radio frequency amplifier when the volume of reproduced sound exceeds a predetermined signal level.

8. A radio broadcast receiver including a radio frequency amplifier, adetector, and an audio frequency amplifier, a radio frequency energy collecting circuit connected with said radio frequency amplifier, an auxiliary rectifier, said auxiliary rectifier having its input terminals capacitively coupled with the output of said audio frequency amplifier, means in the input circuit ofthe auxiliary rectifier for suppressing the passage of unrectifi'ed audio frequency current through the auxiliary rectifier and means controlled by the output circuit of said auxiliary rectifier for effecting a detuning of said radio frequency ampilfier when the volume of reproducedsound exceeds a predetermined signal level;v

In testimony whereof I affix my signature.

. ERNEST R. HENTSGHEL. 

